Today's optical communication networks require the management of a large number of optical fiber interconnections. In many of these interconnections, the transmitted and received signals are run in two separate fibers. Bi-directional communication, where the upstream and downstream signals are running inside a single fiber, is an effective way to reduce the number of fibers used in a fiber-optic communication network. The key for implementing such bi-directional communications is to effectively separate and combine the upstream and downstream signals. One approach to separating and combining upstream and downstream signals is to add optical circulators to each end of a fiber.